Synchronized scanning triangulation in serts the scanning mirrors in the projected light path and the received light pa th,thus the changed angles for the projected light and the received light are th e same when the scanning mirrors are rotated.This synchronized scanning mechanism expands the m easurement field and is adopted in the large distance measurement.In the model of traditional synchroni zed scanning triangulation measurement system,the thickness of rotated mirror is assumed to be zero and th e trajectory of the 3D scanning point is modeled as a circle.However,this simplified assumption deteriorates the precision of the system.In this paper,the thickness of the rotated mirror besidesf other geometry parame ters is considered.The 3D measured point is established with the 14parameters,which describe the position and pose of different parts.Through the simulation,we find that the system′s error could achieve 200mm,when the t hickness of the rotating mirror is 1mm.This error can not be omitted for measuring general objects.In addition,the model′s 3D point for the same pixel position is a circle with the moving center instead of a constant position .This model describes the trajectory more precisely than traditional model.Finally,the prototype system is designed a nd the experimental results show that the method is feasible.